Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!pacbell!att!chinet!mcdchg!ddsw1!ddsw1!vpnet!jms
From: jms@vpnet.UUCP (Jon Schattke)
Newsgroups: comp.sys.ibm.pc
Subject: Re: BIOS Shadowing / Memory usage???
Message-ID: <[659.3]comp.sys.ibm.pc;1@vpnet.UUCP>
Date: 22 Jul 89 10:00:10 GMT
References: <6541@athertn.Atherton.COM> <1288@crdgw1.crd.ge.com>
Lines: 15

>From: stenstro@algol.crd.ge.com [Ross Stenstrom]
>So, what IS shadowing anyway.  Somebody must have come up with it for a
>reason, you would think... ?
Shadowing refers to the process of copying the ROMs into DRAM at boot-up.
It effectively makes things from ROM run about 1.5-2 times faster (because
it's very difficult to get EPROMs below about 200ns access, while DRAM at
80ns isn't _too_ expensive).
Shadowing is especially important for 32bit systems (80386), because then
the system can have only an 8-bit wide ROM (and cost less).

Ain't ya glad you asked?
---
Jonathan Mark Schattke	                        There is _always_ one more bug.
jms@vpnet.UUCP	                If u cn rd ths, u 2 cn bcum a prgrmr & mk bg $.
      VPNET is a free-to-users public-access system in a Chicago Suburb.